1. Field of the Invention
The present invention relates to an apparatus for removing the insulating jacket from cable, and more particularly to a cable insulation stripping machine for stripping the outer insulation from multi-conductor cables.
2. Description of the Related Art
A very common activity for technicians installing electrical equipment is stripping the insulating jacket from cables and wires. Electrical cables are made up of one or more conductors contained in an insulating jacket. The jacket is typically made of an elastomeric material, such as neoprene rubber, silicon rubber, or a polymeric material such as Polyvinylidene Fluoride (PVDF). Electricians strip the insulation from cables in order to expose the conductors. It is necessary to gain access to the conductors in order to connect cables carrying electrical power, control, and other signals to electrical equipment.
Removing the outer insulation from large multi-conductor cables is a particularly onerous task. Multi-conductor cables consist of two or more insulated conductors contained in an outer insulating jacket. Multi-conductor cable may also contain filler, which is material added to occupy the interstitial spaces between the conductors to give the multi-conductor cable a round shape. A typical manual process for removing the outer jacket involves making one or more longitudinal cuts into the outer jacket using a sharp knife and then pulling the jacket away from the cable until the desired length of the internal conductors is exposed. An electrician performing this operation must be careful when making these cuts on a multi-conductor cable not to cut through the insulation on the inner conductors, because doing so would compromise the insulation on these conductors producing possible short circuits during use. For large size electrical conductors, pulling the outer jacket away from the conductors in the jacket may be physically demanding because of the difficulty in flexing the thick outer jacket material and because the jacket adheres to the filler material inside the cable. Removing the cut insulation may be made easier by making multiple cuts into the insulation, allowing the jacket insulation to be removed in narrow strips. However making the additional cuts requires additional time and labor by the electrician, and increases the likelihood of cutting into the insulation of the inner conductors, or of cutting the conductors themselves.
When completing a large installation, the need to strip insulation from both ends of large numbers of cable requires substantial time and labor and adds significantly to both the expense and the completion time for a construction project. In addition, removing the heavy insulation is physically taxing and may result in repetitive motion injuries as well as injuries of other types to the hands and wrists of the electrical installers.
Mechanical or electrically operated machines to strip the outer jacket from multi-conductor cables can speed up the stripping task and make the task less physically demanding. Typically, devices for stripping cable utilize blades to cut through the insulation along the length of the cable and may also include a mechanism for separating the cut insulation from the cable. Because different sizes and types of multi-conductor cable have different diameters, different thickness of insulation, and different arrangements of the internal conductors, these devices may need to make adjustments to the positions of the cutting blades and to other parts of the devices to properly strip the outer insulating jacket from the cable without also cutting through the insulation of the internal conductors or through the conductors. Making these adjustments may increase the time spent stripping the cable or may alternatively result in technicians attempting to strip the jacket from a multi-conductor cable using an inappropriate blade adjustment or setting. An inappropriate setting may require repeating the stripping operation, may damage the cable so that the cable must be discarded, or may even result in installing the cable with damage to the inner conductor insulation, leading to electrical short circuits and the risk of fire, shock, equipment downtime, and damage to equipment.
German Patent No. 3,412,044, published Oct. 3, 1985, describes a device for removing insulation from cables for recycling. The cable stripper described in this publication converts the conductor and insulation of the cable to granular form for recycling, rather than removing the outer cable jacket to leave the internal conductors intact.
Thus, a cable insulation stripping machine solving the aforementioned problems is desired.